Watt-maker

I'm surprised that the super duty has the same frontal area rating unless its a F550.

smokeywren

I don't know why the F-550 has a higher frontal area limit than the F-450, other than the industry standard formula for computing GCWR for class 5 trucks assumes a class 5 truck could often be used to haul or drag a 12-foot tall cargo box that has a lot more frontal area than 60 sq ft. I thought that break between light duty and medium duty trucks was between Class 5 and Class 6, but maybe it's between Class 4 and Class 5?

Frontal area is part of the computation to arrive at GCWR. GCWR has several components, including engine power and torque, axle ratio, speed, and frontal area. The GCWR on a new F-250 diesel with standard axle ratio is 23,500 pounds. That 23,500 pounds is used in advertising the towing capacity of the F-250, so Ford wants it as high as they can get it. In testing to confirm GCWR, the engineers load the truck and trailer down to the GCWR with a trailer that has exactly 60 sq ft frontal area, then drive it at a certain speed up a certain grade for a certain time. If the truck can maintain the minimum speed required, and nothing overheats or breaks on that run, then they increase weight and repeat the test. They continue the test until something overheats or breaks, or the tow vehicle won't maintain the required speed up the grade, then they back off on the weight a bit and that's the certified GCWR.

When doing the GCWR test, the truck has to overcome the grade and mechanical drag as well as the aerodynamic drag. If you increase the aerodynamic drag by increasing the frontal area, you'll decrease the GCWR. So they maintain frontal area at the standard 60 sq ft, regardless of whether the test vehicle is an Escort or a SuperDuty.

That's another reason the "tow rating" is overstated. Factory tow rating is GCWR minus the weight of the tow vehicle. So tow rating assumes a trailer with not more than 60 sq ft frontal area. All 5ers and most TTs have frontal area more than 60 sq ft, so you can't expect to tow a full-profile 5er that weighs anywhere close to the tow rating without being overloaded.

Does anyone know the speed and grade the engineers use in the computation of GCWR? I suspect its 55 MPH on an 8 percent grade, but that's just a guess based on logic.

RedOne

I found this explaination of frontal area on the RV towing guide from Ford. Still says 60 SQ FT...
https://www.fleet.ford.com/showroom/...ng%20Guide.pdf

Page 18

Frontal Area

is the total area in square
feet that a moving vehicle
and trailer exposes to
air resistance. The chart
shows the limitations that
must be considered in
selecting a vehicle/trailer
combination. Exceeding
these limitations may
significantly reduce the
performance of your
towing vehicle. Selecting
a trailer with a low-drag,
rounded front design will
help optimize performance

and fuel economy.

brulaz

Thought I'd try to answer your question by looking up the SAE J-2807A specs online. But the specs are a $66 download: sae.org/j2807_201205

Then I looked around and discovered that Ford has changed its mind and decided to postpone its usage of the SAE towing procedures until after 2013. So the SAE procedures are irrelevant anyway.

But I did find this old article that says something about a 7% grade for the SAE procedure, but who knows what Ford is using:www.pickuptrucks.com

Buck50HD

Thanks for the info guys. I hadn't seen the trailering guide and feel better knowing that the super duty has the same written limitation. Probably just intended to improve tow ratings by limiting drag in the tests.

Bennybone

Does it say anything about tandem towing....

I like to pull my TT and jetski behind the TT, my frontal drag is not much but I sure am long and heavy.



BB

tomb1269

Depends on the Montana. In 2005 the Montana was also made in a TT the bigger ones weighted in over 8000lbs. If done properly you could get a way with it on an F150 FX4 Screw with 18in. My 2005 has hauled it to the site its at and it a hell of a load. If you were going to tow it regularly you'd have to keep your additional weight (people, gear, etc) down around 1200 not to exceed GCWR of 15000 and only about half of that can be in the truck (i.e. 500 to 600 in the truck the rest in the trailer). Its my parents trailer and it does not get towed. Personally, I would stay down around 6000 to 7000 lbs dry on a TT at most to tow behind my F150.